Retractable drill collar stabilizer



y 1966 J. M. KELLNER 3,259,193

RETRACTABLE DRILL COLLAR STABILIZER Filed Feb. 9. 1960 2 Sheets-Sheet 1FIG. I

Jackson M. Kellner Inventor By 9... i. Q..J Attorney y 5, 1965 J. M.KELLNER 3,259,193

RETRACTABLE DRILL COLLAR STABILIZER Filed Feb. 9, 1960 2 Sheets-Sheet 2PENDULUM FORCE FIG. 4

N MITTED AXALLY TRA s RESULTANT FORCE FORCES Jackson M. Kellner InventorBy %-.HJ 8. Q). Attorney United States Patent 3,259,193 RETRACTABLEDRILL COLLAR STABILIZER Jackson M. Kellner, Tulsa, Okla, assignor toEsso Production Research Company, a corporation of Delaware Filed Feb.9, 1960, Ser. No. 7,671 8 Claims. or. 166237) The present inventionrelates to apparatus useful for drilling boreholes in the earth and moreparticularly relates to an improved drill collar stabilizer for use inthe rotary drilling of such boreholes. In still greater particularity,the invention relates to a retractable, hydraulically-actuated drillcollar stabilizer free of many of the disadvantages which have limitedthe application of drill collar stabilizers in the past.

The successful rotary drilling of oil wells, gas wells, and similarboreholes in the earth requires the application of high pressures to theformation beneath the drill bit. For this reason, it is conventional toprovide a series of heavy drill collars in the drill string just abovethe bit. The drill collars thus employed may weigh from 50,000 to100,000 pounds or more and may extend several hundred feet up the drillstring. The weight of the drill collars supplies the necessary pressureand at the same time holds the drill pipe in the upper part of the holein tension so that it has little tendency to buckle or flex as it isrotated. The collars themselves, however, are under compression andhence do tend to buckle to some extent. This buckling action, combinedwith the tendency of dipping, laminated strata to deflect the bit, oftenleads to the drilling of crooked, sloping boreholes. In such a borehole,the weight of the drill collars below the point of last contact with theborehole wall may be divided into two components: one acting along theaxis of the collars and a second acting normal to the first toward thelow side of the hole. This second component is generally referred to asthe pendulum force. The portion of the drill string above the point oflast contact which is not in tension results in an additional forcewhich is transmitted axially by the collars and is in effect appliedfrom the point of contact at an angle greater than the deviation angle.Ignoring effects due to heterogeneity of the rock being drilled, the bitwill advance in the direction of the resultant of the pendulum force andthe forces transmitted axially by the drill collars. If the angle of theresultant to the vertical exceeds the deviation angle, continueddrilling will result in greater deviation; whereas continued drillingwill produce a decrease in deviation if the angle of the resultant tothe vertical is less than the deviation angle. The angle which theresultant makes with the vertical can be changed by changing thependulum force, by changing the force transmitted axially by the drillcollars, or by changing the direction in which the axially-transmittedforce is applied to the bit.

The normal method for correcting deviation is to place a drill collarstabilizer in the drill string at an intermediate point between twodrill collar sections in order to hold the drill collars away from theborehole wall. This raises the point of contact between the drill stringand wall and thus increases the magnitude of the pendulum force at thebit. It also decreases the angle to the vertical at which the forcestransmitted axially by the drill collars are applied to the bit. Themore nearly vertical resultant force acting on the bit tends to force itto drill in a more vertical direction. Continued use of a drill collarstabilizer in this manner will in most cases eventually result instraightening of the borehole.

The drill collar stabilizers employed in the manner set forth above aregenerally tubular members provided with lateral projections which, whenthe stabilizer is connected between adjacent drill collars, will bear onthe sloping ice borehole wall and hold the collars away from the wall.The outer diameter of such a stabilizer should be slightly smaller thanthe diameter of the borehole in order to permit continuous downwardmovement of the drill collar and stabilizer as the drilling operationprogresses and yet should be large enough to permit suspension of thedrill collars as far from the borehole wall as possible. Stabilizersemployed heretofore have generally had fixed projections or ribs made ofrubber, steel or a similar material. Experience has shown thatstabilizers of this type are not wholly satisfactory because theprojections or ribs tend to snag the walls of the borehole during tripsto and from the surface. This often results in damage to the walls andin some cases may cause the drill string to become stuck in theborehole. Stabilizers provided with projections which will deflect oncontact with the borehole during trips into and out of the borehole havebeen suggested recently but have been found equally unsatisfactory. Itis diflicult to make the projections resilient enough to avoid damage tothe borehole wall during tripping and yet make them stiff enough toresist the weight of the drill collar-s against the wall in a slopingborehole. Moreover, resilient projections or ribs of rubber or similarmaterial are frequently cut and abraded upon contact with shale-s andother hard strata during tripping.

The present invention provides a new and improved drill collarstabilizer having retractable projections or shoes which willeifectively support the drill collars for stabilization purposes and yetcan easily be withdrawn from the borehole without injuring the shoes ordamaging the borehole wall. The improved stabilizer thus providedincludes a hollow mandrel having a passage through which drilling fluidcan be admitted to an annular sleeve mounted on the mandrel. The sleevecontains a plurality of openings in which are positioned extensibleshoes held in place by rubber or similarly elastic collars. Circulationof drilling fluid through the drill string results in a pressuredifferential across the shoes which forces them outwardly into anextended position. When fluid circulation is interrupted and thepressure equalized, rubber collars surrounding the shoes force them backinto the retracted position. The stabilizer thus supports the drillcollar-s away from the borehole wall as long as drilling fluid is beingcirculated and is automatically retracted for tripping purposes when thefluid pressure is reduced. This permits rapid tripping into and out ofthe borehole, reduces wear and abrasion of the stabilizer shoes, anddecreases the likelihood of damage to the borehole wall during tripping.

The exact nature and objects of the invention can best be understood byreferring to the following detailed de scripti-on of a preferredembodiment of the improved drill collar stabilizer and to theaccompanying drawings, in which:

FIG. 1 is an elevational View, partially in section, of a drill collarstabilizer provided with hydraulically-actuated shoes constructed inaccordance with the invention;

FIG. 2 is a cross-sectional view through the apparatus of FIG. 1 takenalong the line 22;

FIG. 3 is a partially-sectioned view of a shoe slightly modified fromthat shown in FIGS. 1 and 2; and,

FIG. 4 is a small scale elevational view of the lower end of a rotarydrill string provided with a drill collar stabilizer for straighteningthe borehole.

Turning first to FIG. 1 of the drawing, the tool depicted thereinincludes a mandrel 11 which is generally cylindrical in shape andcontains an axial passage 12 through which fluids may flow from one endof the tool to the other. The mandrel is provided with means at itsupper and lower ends for connecting the tool at an intermediate positionwithin a conventional rotary drill string. As depicted in the drawing,the mandrel includes a standard API pin joint 13 at its lower end and aseparate API box joint 14 connected to the upper end of the mandrel bythreads or equivalent means 15 in order to permit disassembly of thetool when desired. Mandrel 11 is divided axially into three integralsections, a lower section 16 of relatively large diameter located justabove pin joint 13, an intermediate section 17 separated from lowersection 16 by tapered shoulder 18, and an upper section 19 between boxjoint 14 and intermediate section 17 which is separated from theintermediate section by a second tapered shoulder 20. Fluid passage 21extends laterally from axial passage 12 to the outer surface of themandrel within intermediate section 17. Fluid grooves 22 and 23 arelocated on the outer surface of the mandrel respectively above and belowthe outlet of passage 21 for stress relief purposes. The upper end oflower mandrel section 16 is provided with a notched shoulder 24.

Sleeve 25 in FIG. 1 of the drawing is a tubular member carried onintermediate section 17 and upper section 19 of mandrel 11. The sleeveis divided axially by sloping internal shoulder 26 into an upper section27 and a lower section 28. The inner diameter of integral sleevesections 27 and 28 are slightly larger than the outer diameters ofmandrel section 19 and 17 respectively in order to permit the sleeve torotate and move axially on the mandrel. Wiper ring 29 and seal ring 30of rubber or similar elastic material are set in annular grooves on theinner surface of the sleeve near the upper end thereof and provide afluid-tight seal between the sleeve and mandrel. Passage 31 permits theescape of fluids entrapped between the rings. Similar rings 32 and 33and passage 34 are located near the bottom of the sleeve for likepurposes. As shown, the rings also serve as bearings between the mandreland sleeve. Separate bearings may be provided if desired. In itslowermost position, the axially slidable sleeve 25 seats upon slopingshoulder 18 on the mandrel and is supported thereby. Box joint 14extends laterally beyond the mandrel and thus serves to retain thesleeve when it is in its uppermost position. The lower edge of thesleeve is provided with keys 35 so that the mandrel and sleeve may belocked together and rotated in a counterclockwise direction if desired.The faces of the keys are tapered to permit clockwise rotation of themandrel independently of the sleeve.

Sleeve 25 is provided with a plurality of lateral openings in which theextensible shoes utilized are positioned. It is preferred that theopenings be spaced at regular intervals around the sleeve and arrangedin a staggered pattern along the vertical axis of the sleeve. Althoughthe stabilizer depicted in the drawing is provided with six extensibleshoes, it will be understood that the device is not limited to six shoesand that a greater or lesser number may be utilized.

Positioned in each of the aforementioned lateral openings in sleeve 25is a supporting ring 36 which is provided with an external shoulder 37.Shoulder 37 mates with a similar shoulder on the wall of the opening andthus serves to retain ring 36 within the opening. The supporting ring isprovided with an annular internal shoulder 38 which separates theopening in the ring into an inner section and an outer section ofreduced diameter. Shoe 39 having a flange 40 around the back portionthereof is positioned in ring 36 so that the body of the shoe extendsinto theouter section of the ring opening. Flange 40 on the shoeprevents over-extension by contacting shoulder 38 in the supportingring. An elastic collar 41 is bonded to the outer surface of the shoeand the inner surface of the supporting ring. The collar may be made ofrubber, plastic or similar resilient material. Neoprene and nitrilerubber have been found particularly attractive because of theirresistance to deterioration in the presence of crude oils. Collar 41should be bonded between the ring and shoe in a manner such that theelasticity of the collar tends to hold the shoe in a retracted positionWithin the ring. A material having a sufficient modulus of elasticity topermit extension of the shoe at low differential pressures and capableof withstanding the shear stresses encountered at higher operatingpressures should be employed. Good bonding properties to metal aredesirable.

As shown more clearly in FIG. 2 of the drawing, the rear surface of shoe39 is arched and has a radius essentially the same as the inner radiusof sleeve 25. In like manner, supporting ring 36 conforms to the innerwall of the sleeve. When the apparatus is assembled as shown in thedrawing, mandrel 11 prevents movement of the ring with respect to thesleeve and retains the shoe within the ring. The diameter of thestabilizer with the shoes extended should be slightly less than thediameter of the bit with which the stabilizer is to be used.

FIG. 3 of the drawing depicts a preferred shoe embodiment in which theouter surface of the shoe is provided with a hard surface 42 whichextends beyond the edge of the shoe to form a lip 43. This lip protectsthe bond between shoe 39 and collar 41 and prevents failure of the bonddue to wear and abrasion. The elastic collar, in the embodiment shown inFIG. 3, is provided with a lip 44 which covers shoulder 38 in supportingring 36 and thus assures a fluid-tight seal between the shoe and ring.Such a seal prevents excessive pressure differentials across the collarand permits the use of operating pressures which might not otherwise befeasible. A separate sealing ring of rubber or other material may beprovided to effect a seal between the shoulder and flange if desired.

The operation of the improved drill collar stabilizer of the inventionfor straightening a crooked borehole can best be seen by referring toFIG. 4 of the drawing. After it has become apparent that the bore holehas deviated from the vertical during the drilling operation, the drillstring is withdrawn from the hole. The hole is then surveyed todetermine the points at which it changes in slope. Conventionalinclinometers and similar instruments can be employed for this purpose.The information thus obtained, coupled with information as to thetendency of the drill collars to sag under their own weight, will permitcalculation of the distance above the bit at which the stabilizer shouldbe placed in order to suspend the maximum length of drill collarsbetween the bit and stabilizer out of contact with the borehole wall.Standard tables giving these distances for variou drill collar and bitsizes and various deflection angles are available and will be familiarto those skilled in the art. The tables also generally indicate theextent to which the weight on the bit can be increased withoutincreasing deviation if a stabilizer is used. The stabilizer is theninserted at the proper place in the drill string and the string islowered back into the borehole.

After the drill string containing the stabilizer has been lowered inplace in the borehole, drilling fluid is circulated downwardly throughthe string and up the annulus. Fluid flowing through mandrel 11 of thestabilizer enters passage 21 and the space between the outer surface ofthe mandrel and the sleeve. Pressure behind the stabilizer shoe istherefore essentially the same as that within the mandrel. The pressureon the face of the shoes outside the sleeve, on the other hand, will beconsiderably less due to the pressure drop across the nozzles of thebit. In response to this difference in pressure, the shoes are forcedoutwardly until flange 40 contacts shoulder 38 on the retaining ring 36.Extension of the shoes in this manner forces the stabilizer away fromthe borehole walls so that the lower portion of the drill string issuspended between the stabilizer and bit as shown in FIG. 4 of thedrawing. The last point of contact between the drill string and boreholewall is thus higher than it would be in the absence of the stabilizer.This increases the pendulum force on the bit and decreases the angle tothe vertical at which forces are transmitted axially by the drillcollars to the bit. As a result, the angle of the resultant force to thevertical is reduced.

Qn resuming rotation of the drill string after the stabllizer has beenplaced in the borehole as described above, the stabllizer mandrelrotates Within the sleeve. The,

change in the forces acting on the bit clue to the presence of thestabilizer causes the bit to drill in a more nearly vertical direction.As drilling progresses and the drill string moves downwardly, pressureexerted on the sleeve by the lower end of the box joint connected to theupper end of the mandrel forces the sleeve downwardly. The shoes incontact with the borehole walls slide against the wall. Wear on theouter surface of the shoes is generally insignificant because of theslow relative motion between the shoes and the Wall and because of theabsence of high contact pressures between the shoe and the wall. Theouter surface of the shoe and collar may, however, be sheathed with anabrasion-resistant material as pointed out heretofore.

Continued drilling of the borehole with the stabilizer in place willnormally result in a continuous decrease in the inclination of the holeuntil it is substantially vertical and the stabilizer shoes no longerbear on the borehole wall. Drilling with the stabilizer in place afterthe borehole has been straightened ha no adverse effect and henceimmediate removal of the stabilizer is unnecessary. In many operationswherein it is known that borehole deflection is likely to occur, it isoften preferred to drill the entire borehole using the stabilizer placednear the upper end of the drill collar section. When thus used, thestabilizer will begin to correct or control deviations inthe boreholebefore they might otherwise be detected. Repeated surveying of the holecam sometimes thus be avoided.

When the circulation of drilling fluid through the drill string ishalted in order to permit withdrawal of the drill string from theborehole, the pressure on the inside and outside surfaces of the shoesequalize. The shoes are thereupon retracted by the elastic collar whichconnects the shoes and retaining rings in the sleeve. 'The drill stringthereafter can be pulled out of the borehole without danger of injuringthe stabilizer shoes or damaging the borehole walls. It is preferredthat the shoes in the retracted position in the supporting rings on thesleeves extend slightly beyond the outer surface of the sleeve as shownin the drawing in order to avoid sticking of the sleeve in the boreholedue to the differential effect sometimes observed when smooth columnscontact the borehole walls. An advantage of the hydraulically-actuatedshoes employed in the stabilizer of the invention is that the shoes maybe extended to free the drill string should it become stuck duringtripping. Pressure drop across the nozzlw of the bit under full fluidpressure permits extension of the shoes regardless of the position ofthe drill string in the bore-hole.

The retractable drill collar stabilizer of the invention may be operatedover a wide range of fluid pressures. It is generally preferred thatflange 40 on the rear surface of each shoe mate with shoulder 38 on thecorresponding supporting ring to form a fluid-tight seal where very highfluid pressures are to be used. This restricts the pressure applied tothe elastic collar to that amount necessary to overcome the resistanceof the collar and move the shoe outwardly against the shoulder. Fluidpressures Well in excess of those at which the collar would otherwisefail or be torn loose from the shoe or ring can thus be safely used.

In the event that the stabilizer should for some reason become stuck inthe borehole so firmly that it connot be extricated by extension of theshoes, it can be removed by lowering a washover device over it .andmilling off the projection on the surface of the sleeve. Notches on theupper edge of the section of the mandrel and the keys on the lower edgeof the sleeve will lock together and prevent the sleeve from rotating onthe mandrel as the projections are milled. The shoes and retaining ringscan be replaced following such an operation without the necessity forreplacing the sleeve and mandrel and hence the damage to the stabilizeris minimized. Because of the very large forces which can be exertedagainst the borehole wall by 6 extending the shoes when the drill stringbecomes stuck in the borehole, the necessity for carrying out suchwashover operations rarely arises.

What is claimed is:

:1. Rotary drilling apparatus which comprises:

a mandrel provided with means at its upper and lower ends forconnect-ing said apparatus at an intermediate point in a rotary drillstring, said mandrel including a longitudinal passageway for thetransmission of drilling fluid and a lateral passageway extendingthrough the mandrel wall from said longitudinal passageway to a port inthe outer surface of said mandrel;

a tubular sleeve slidably mounted on said mandrel over said port forlongitudinal and rotational movement thereon, said sleeve containing .aplurality of vertically and circumferentially spaced wall openings topermit the centering of said sleeve and mandrel in the borehole by shoesmounted in said openings;

a plurality of laterally-extensible shoes positioned in said wallopenings in said sleeve;

an elastic member bonded to said shoe within each of said wall openingsand connected to the surrounding sleeve, said elastic member forming afluid-tight seal about said shoe and biasing said shoe in a normallyretracted position with respect to said sleeve while permittingextension of said shoe in response to fluid pressure between said sleeveand mandrel;

means for limiting the extension of said shoes and thereby preventingthe anchoring of said apparatus in said borehole;

upper and lower seal members positioned between said sleeve and mandrelrespectively above and below said wall openings;

and means limiting longitudinal movement of said sleeve with respect tosaid mandrel.

2. Rotary drill-ing apparatus which comprises:

a tubular mandrel provided with means near the upper .and lower endsthereof for connecting said mandrel at an intermediate point in a rotarystring, said mandrel including a passageway extending through themandrel wall to a port in the outer surface thereof;

a tubular sleeve sl-idably mounted on said mandrel over said port forlongitudinal and rotational movement thereon, said sleeve containing aplurality of wall openings vertically and circumferentially spaced topermit centering of the sleeve and mandrel in a borehole by means ofshoes mounted in said openings;

a supporting ring seated in each of said wall openings in fluid-tightrelationship to said sleeve;

a laterally-extensible shoe positioned within each of said supportingrings;

an elastic member bonded to said shoe and to said supporting ring ineach of said wall openings to form a fluid-tight seal, said elasticmember biasing said shoe in a normally retracted position with respectto said sleeve while permitting extension of said shoe in response tofluid pressure bet-ween said sleeve and mandrel;

means for limiting the extension of said shoes with respect to saidsleeve and thereby preventing the anchoring of said apparatus in saidborehole;

upper and lower seal members positioned between said sleeve and mandrelrespectively above and below said wall openings;

and means for limiting longitudinal movement of said sleeve with respectto said mandrel.

3. A drill collar stabilizer comprising:

an elongated tubular mandrel provided with means for connecting saidmandrel at an intermediate point in a rotary drill string, said mandrelincluding an intermediate section of reduced diameter and a lateralpassageway extending through the mandrel wall within said intermediatesection;

a longitudinally-extending sleeve mounted on said intermediate sectionofsaid mandrel for longitudinal and rotational movement thereon, saidsleeve containing a plurality of wall openings vertically andcircumferentially spaced to permit centering of the sleeve and mandrelin a borehole by means of shoes mounted in said openings;

a supporting ring mounted in each of said wall openings in fluid-tightrelationship to said sleeve, each of said supporting rings containing aninternal shoulder located near the outer face of said ring;

a laterally-extensible shoe mounted in each of said supporting rings,each. of said shoes including a section having an outer diameter greaterthan the inner diameter of said shoulder on said ring;

an elastic member bonded to the outer periphery of said shoe and theinner periphery of said ring within each of said wall openings to form afluid-tight seal, said elastic member biasing said shoe in a normallyretracted position with respect to said ring while permitting extensionof said shoe with respect to said ring in response to fluid pressurebetween said sleeve and mandrel;

and upper and lower seal members positioned between said sleeve andmandrel respectively above and below said wall openings.

4. A drill collar stabilizer which comprises:

an elongated tubular mandrel provided with means near the upper andlower ends thereof for connecting said mandrel at an intermediateposition within a rotary drill string, said mandrel including anintermediate section of reduced diameter and a lateral passagewayextending through the mandrel wall within said intermediate section;

a longitudinally-extending sleeve slidably mounted on said intermediatesection of said mandrel for longitudinal and rotational movementthereon, said sleeve containing a plurality of wall openings verticallystaggered and spaced at circumferential intervals about the sleeve topermit centering of the sleeve and mandrel in a borehole by means ofshoes mounted in said openings;

a supporting r'ing mounted in each of said wall openings in fluid-tightrelationship to said sleeve, each of said supporting rings containing aninternal shoulder located near the outer face of said ring;

a laterally-extensible shoe positioned within each of said supportingrings, each of said shoes including a rear flange having an outerdiameter greater than the inner diameter of said shoulder on said ring;

an elastic sleeve bonded to the outer periphery of said shoe and theinner periphery of said ring in each of said wall openings to form afluid-tight seal, said elastic member biasing said shoe in a normallyretracted position with respect to said ring while permitting extensionof said shoe with respect to said ring in response to fluid pressurebetween said sleeve and mandrel;

and upper and lower seal members positioned between said sleeve andmandrel respectively above and below said wall openings in said sleeve.

5. A drill collar stabilizer comprising:

an elongated tubular mandrel provided with means for connecting saidmandrel at an intermediate point within a rotary drill string, saidmandrel including an intermediate section of reduced diameter and alateral passageway extending through the mandrel wall within saidintermediate section;

a longitudinally-extending sleeve mounted on said intermediate sectionof said mandrel for longitudinal and rotational movement thereon, saidsleeve containing a plurality of wall openings vertically staggered andequally spaced circumferentially whereby said sleeve (3 and mandrel arecentered in the borehole by shoes mounted in said openings; .alaterally-extensible shoe mounted in each of said wall openings;

5 an elastic member bonded to each of said shoes and connected to thesurrounding sleeve to form a fluidtight seal within each of said wallopenings, said elastic member biasing said shoe in a normally retractedposition with respect to said sleeve while permitting extension of saidshoe in response to fluid pressure between said sleeve and mandrel;

means associated with said shoe and sleeve for limiting the extension ofsaid shoes and thereby preventing the anchoring of said stabilizer insaid borehole;

upper and lower seal members positioned between said sleeve and mandrelrespectively above and below said wall openings;

means for limiting longitudinal movement of said sleeve on said mandrel;

and means for interlocking said sleeve and mandrel to prevent clockwiserotation of said sleeve with respect to said mandrel when said sleeve isin the lowermost position on said mandrel.

6. A shoe assembly for use on a down-hole tool containing a lateralopening in which a hydraulically extensible shoe is positioned whichcomprises:

a supporting ring for retention in said opening, said ring having anouter section and an inner section of 30 enlarged diameter separatedfrom said outer section by an internal shoulder; a shoe mounted withinsaid ring and provided with a rear section for engaging said shoulder insaid ring; and an elastic collar bonded to said ring and said shoe forretaining said shoe in a normally retracted position with respect tosaid ring while permitting extension of said shoe in response to fluidpressure from within said ring.

7. An assembly as defined by claim 6 wherein said elastic member extendsover said shoulder in said ring to effect a seal between said shoulderand said rear section on said shoe when the shoe is in its outermostposition with respect to said ring.

8. A shoe assembly for use on a down-hole tool containing a lateralopening in which a hydraulically extensible shoe is positioned whichcomprises:

a supporting ring for retention in said opening;

a shoe mounted within said supporting ring;

an elastic collar bonded to the inner surface of said supporting ringand the outer surface of said shoe for retaining said shoe in a normallyretracted position with respect to said ring while permitting extensionof said shoe relative to said ring in response to fluid pressure;

and means independent of fluid pressure for preventing the extension ofsaid shoe with respect to said ring beyond a predetermined point.

References Cited by the Examiner UNITED STATES PATENTS 2,212,067 8/1940HOfiOSs 17538l 2,316,409 4/1943 Downing 255-1.6 2,572,307 10/1951 Brownet al 3084 2,876,992 3/1959 Lindsay 2551.6 2,891,769 6/1959 Page et a1.2551.6 3,023,821 3/1962 Etherington l7576 CHARLES E. OCONNELL, PrimaryExaminer.

BENJAMIN HERSH, BENJAMIN BENDETT,

Examiners.

R. E. FAVREAU, J. A. LEPPINK, G. T. BROWN,

r Assistant Examiners.

1. ROTARY DRILLING APPARATUS WHICH COMPRISES: A MANDREL PROVIDED WITHMEANS AT ITS UPPER AND LOWER ENDS FOR CONNECTING SAID APPARATUS AT ANINTERMEDIATE POINT IN A ROTARY DRILL STRING, SAID MANDREL INCLUDING ALONGITUDINAL PASSAGEWAY FOR THE TRANSMISSION OF DRILLING FLUID AND ALATERAL PASSAGEWAY EXTENDING THROUGH THE MANDREL WALL FROM SAIDLONGITUDINAL PASSAGEWAY TO A PORT IN THE OUTER SURFACE OF SAID MANDREL;A TUBULAR SLEEVE SLIDABLY MOUNTED ON SAID MANDREL OVER SAID PORT FORLONGITUDINAL AND ROTATIONAL MOVEMENT THEREON, SAID SLEEVE CONTAINING APLURALITY OF VERTICALLY AND CIRCUMFERENTIALLY SPACED PLURALITY OFVERTIPERMIT THE CENTERING OF SAID SLEEVE AND MANDREL IN THE BOREHOLE BYSHOES MOUNTED IN SAID OPENINGS; A PLURLAITY OF LATERALLY-EXTENSIBLESHOES POSITIONED IN SAID WALL OPENINGS IN SAID SLEEVE; AN ELASTIC MEMBERBONDED TO SAID SHOE WITHIN EACH OF SAID WALL OPENINGS AND CONNECTED TOTHE SURROUNDING SLEEVE, SAID ELASTIC MEMBER FORMING A FLUID-TIGHT SEALABOUT SAID SHOE AND BIASING SAID SHOE IN A NORMALLY RETRACTED POSITIONWITH RESPECT TO SAID SLEEVE WHILE PERMITTING EXTENSION OF SAID SHOE INRESPONSE TO FLUID PRESSURE BETWEEN SAID SLEEVE AND MANDREL; MEANS FORLIMITING THE EXTENSION FO SAID SHOES AND THERBY PREVENTING THE ANCHORINGOF SAID APPARATUS IN SAID BOREHOLE; UPPER AND LOWER SEAL MEMBERSPOSITIONED BETWEEN SAID SLEEVE AND MANDREL RESPECTIVELY ABOVE AND BELOWSAID WALL OPENINGS; AND MEANS LIMITING LONGITUDINAL MOVEMENT OF SAIDSLEEVE WITH RESPECT TO SAID MANDREL.